Diffusely-reflecting reversible electrochemical mirror

Abstract

A reversible electrochemical mirror device includes a substantially transparent first electrode having a textured surface, and a second electrode which may be distributed in localized areas. An electrolytic solution, disposed between the first and second electrodes, contains ions of a metal which can electrodeposit on the electrodes. A negative electrical potential applied to the first electrode causes deposited metal to be dissolved from the second electrode into the electrolytic solution and to be electrodeposited from the solution onto the textured surface of the first electrode, thereby affecting the reflectivity of the device for electromagnetic radiation. Because of the textured surface, light striking the first electrode is diffusely reflected, making the device desirable for architectural and automotive glass applications. A surface modification layer applied to the first electrode ensures that the electrodeposit is substantially uniform. A positive electrical potential applied to the first electrode causes deposited metal to be dissolved from the first electrode and electrodeposited from the solution onto the second electrode, thereby decreasing the reflection of radiation by the device.

What is claimed is:  
     
       1. A reversible electrochemical mirror (REM) device for controlling the amount and direction of reflected electromagnetic radiation, comprising: 
       a first substrate which is substantially transparent to at least a portion of the spectrum of electromagnetic radiation;  
       a first electrode disposed on the first substrate which is substantially transparent to the radiation, the surface of the first electrode not adjacent to the first substrate being textured on a microscopic or macroscopic scale;  
       a surface modification layer disposed on the first electrode which substantially conforms to the textured surface;  
       a second electrode;  
       an electrolytic solution disposed between and in electrical contact with the first and second electrodes;  
       a plurality of ions of a metal capable of electrodeposition on the first and second electrodes, the ions being soluble in the electrolytic solution; and  
       a plurality of atoms of said metal disposed on at least one of the first or the second electrode;  
       such that a negative electrical potential applied to the first electrode relative to the second electrode causes deposited metal to be dissolved from the second electrode into the solution and to be electrodeposited from the solution onto the textured surface of the first electrode, the surface modification layer facilitating substantially uniform nucleation of the electrodeposited metal on the first electrode, and  
       such that a positive electrical potential applied to the first electrode relative to the second electrode causes deposited metal to be dissolved from the textured surface of the first electrode and electrodeposited from the solution onto the second electrode, and  
       such that the amount of deposited metal subsisting on the first electrode affects the reflectivity of the device for the radiation, and  
       such that metal deposited on the textured surface of the first electrode reflects radiation incident from at least some directions diffusely.  
     
     
       2. The device of claim  1 , wherein the surface of the first substrate adjacent to the first electrode is textured, the first electrode conforming to the textured surface of the first substrate, and the surface modification layer conforming to the textured surface of the first electrode. 
     
     
       3. The device of claim  1 , wherein the textured surface of the first electrode includes no sharp points or ridges so that the conformal uniformity of the metal layer electrodeposited onto the textured surface is not adversely affected by the texturing. 
     
     
       4. The device of claim  1 , wherein the textured surface of the first electrode comprises a pattern of rounded hills and troughs such that light which is specular when it strikes the textured surface is non-specular when reflected by the textured surface. 
     
     
       5. The device of claim  1 , wherein the first electrode lies in an x-y plane, the textured surface of the first electrode describing a first sine wave along the plane's x-axis and describing a second sine wave along the plane's y-axis such that light that is specular when it strikes the textured surface is non-specular when reflected by the textured surface. 
     
     
       6. The device of claim  1 , further comprising: 
       a second substantially transparent substrate, the second electrode being distributed on the second substrate in localized areas and being substantially transparent to the radiation.  
     
     
       7. The device of claim  6 , wherein the second substrate is an electrically insulating substrate and the second electrode is a continuous electrical conductor. 
     
     
       8. The device of claim  7 , wherein the second electrode is arranged in a conductive mesh or grid pattern. 
     
     
       9. The device of claim  6 , wherein the second electrode is a discontinuous metallic film on a substantially transparent electrical conductor. 
     
     
       10. The device of claim  9 , wherein the discontinuous metallic film of the second electrode is arranged in a dot matrix pattern. 
     
     
       11. The device of claim  6 , wherein the second electrode is an electrically continuous grid of an electrochemically stable metal deposited on the second substrate. 
     
     
       12. The device of claim  11 , wherein the electrochemically stable metal of the second electrode includes at least one metal selected from the group consisting of Au, Cr, Ir, Ni, Os, Pd, Pt, Re, Rh, Ru and stainless steel. 
     
     
       13. The device of claim  6 , filter comprising an underlayer between the second electrode and the second substrate to improve adhesion between the second electrode and the second substrate. 
     
     
       14. The device of claim  13 , wherein the underlayer includes at least one metal selected from the group consisting of aluminum, chromium, hafliumn, molybdenum, nickel, titanium, tungsten and zirconium. 
     
     
       15. The device of claim  1 , wherein the first electrode is disposed uniformly on the first substrate. 
     
     
       16. The device of claim  1 , wherein the first electrode is an electrically conductive oxide coating deposited on the first substrate. 
     
     
       17. The device of claim  16 , wherein the electrically conductive oxide coating is selected from the group consisting of aluminum (doped) zinc oxide, antimony (doped) tin oxide, fluorine (doped) tin oxide, indium oxide, indium tin oxide, fluorine (doped) indium oxide, aluminum (doped) tin oxide, phosphorus (doped) tin oxide, and indium zinc oxide. 
     
     
       18. The device of claim  1 , wherein the surface modification layer is a thin layer of a metal which is electrochemically more stable towards oxidation in the electrolytic solution than the electrodeposited metal. 
     
     
       19. The device of claim  18 , wherein the stable metal layer includes at least one metal selected from the group consisting of Au, Ir, Os, Pd, Pt, Re, Rh and Ru. 
     
     
       20. The device of claim  1 , further comprising an underlayer between the first electrode and the surface modification layer to improve adhesion between the first electrode and the surface modification layer. 
     
     
       21. The device of claim  20 , wherein the underlayer includes at least one metal selected from the group consisting of aluminum, chromium, hafnium, molybdenum, nickel, titanium, tungsten and zirconium. 
     
     
       22. The device of claim  6 , wherein at least one of the first and second substrates are glass. 
     
     
       23. The device of claim  6 , wherein at least one of the first and second substrates are a plastic. 
     
     
       24. The device of claim  23 , wherein the plastic substrates are selected from the group consisting of acrylics, urethanes, polystyrenes, polycarbonates, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, cellulosics, acrylonitrilebutadiene-styrene, polyvinylchloride, thermoplastic polyesters, polypropylene, nylons, polyester carbonates, ionomers, polyethyleneterephthate, and cyclic olefin copolymers. 
     
     
       25. The device of claim  1 , wherein the electrolytic solution is a solution containing water. 
     
     
       26. The device of claim  25 , wherein the electrolytic solution further comprises a gelling agent to form a gel electrolyte. 
     
     
       27. The device of claim  26 , wherein the gelling agent is selected from the group consisting of gelatin, polyacrylamide, polyacrylates derived from polyacrylic acid, polyvinylalcohol, polyvinylpyrrolidone, cellulose derivatives, polyethylene glycols, polyethylene oxides, pectin, tragacanth, alginates, starches, xanthan gum, guar gum, acacia, cetostearyl alcohol, highly dispersed silica, and bentonite. 
     
     
       28. The device of claim  25 , wherein the electrolytic solution is contained within a solid matrix. 
     
     
       29. The device of claim  28 , wherein the solid matrix is selected from the group consisting of finely divided electrically insulating powders, porous polymers, insulating sponges, insulating felts, and ormasils. 
     
     
       30. The device of claim  1 , wherein the electrolytic solution is a non-aqueous solution. 
     
     
       31. The device of claim  30 , wherein the electrolytic solution further comprises an electrochemically inert gelling agent to form a non-aqueous gel electrolyte. 
     
     
       32. The device of claim  31 , wherein the gelling agent is a soluble polymer. 
     
     
       33. The device of claim  32 , wherein the soluble polymer gelling agent is selected from the group consisting of polyacrylamide, polyacrylic acid, polyacrylonitrile, polycarbonate resin, polymethylmethacrylate, polypropylenecarbonate, polyvinylalcohol, polystyrenes, polyvinylchloride, polyvinylidinefluoride, and polyvinylpyrrolidone. 
     
     
       34. The device of claim  30 , wherein the electrolytic solution is contained within a solid matrix. 
     
     
       35. The device of claim  34 , wherein the solid matrix is selected from the group consisting of finely divided electrically insulating powders, porous polymers, insulating sponges, insulating felts, and ormasils. 
     
     
       36. The device of claim  1 , wherein the electrodepositable metal ions are selected from the group consisting of Ag + , Bi 3+ , Cu +/2+ , Cd 2+ , Hg 2+ , In 3+ , Pb 2+ , Sb 3+ , Tl +/3+ , Sn 2+/4+ , and Zn 2+ . 
     
     
       37. The device of claim  1 , wherein the electrolytic solution includes at least one solvent selected from the group consisting of benzonitrile, dimethylcarbonate, dimethylsulfoxide, ethylene carbonate, ethylene glycol, γ-butyrolactone, glycerol, propylene carbonate, sulfolane, tetraglyme, dimethylformamide, and water. 
     
     
       38. The device of claim  1 , wherein the electrolytic solution further comprises a complexing species for chemically stabilizing the electrodepositable metal ion in solution, thereby facilitating the electrodeposition of a substantially uniform layer of the metal on the first electrode and the electrodissolution of that layer. 
     
     
       39. The device of claim  38 , wherein the complexing species is selected from the group consisting of aromatic and olefinic compounds, aromatic nitrites, benzonitrile, aromatic heterocyclic amines, aromatic heterocyclic sulfides, quinoline, aliphatic amines, aromatic amines, organo-nitriles, organo-phosphines, organo-thiols, organo-sulfides, halide ions, polyhydric alcohols, succinimide, and pseudohalides.